Two-dimensional modeling of a glow discharge source for mass spectrometry

Summary form only given. Glow discharge mass spectrometry (GDMS) is now widely used for elemental analysis of various materials. This diagnostic uses a low current discharge in a buffer gas to sputter atoms from a sample to be analyzed. A small density of atoms of the sample are thus introduced into the gas phase. These atoms are ionized in the discharge, and the ions are extracted through a small, rectangular slit leading to a mass spectrometer. Very low absolute detection limits are possible with GDMS's, but many aspects of this diagnostic still require carefully adjustments to achieve good performance. A better understanding especially of the influence of the discharge operating conditions (pressure, current, geometry, ...) on the ion fluxes arriving at the plane of the exit slit is needed. The purpose of the work presented here is to develop such an understanding through a combined experimental and theoretical program, but the work reported here relates mainly to results from the model. The particular conditions we have chosen to study correspond to the commercially available VG9000 spectrometer and Megacell source.